1. Field of the Invention
The present invention relates to an antenna apparatus used for satellite communication or the like and including an antenna rotating in an azimuth angle direction and an elevation angle direction.
2. Description of the Related Art
An antenna apparatus for satellite communication catches or follows a communication satellite by combining the driving of an antenna in an azimuth angle direction with the driving thereof in an elevation angle direction correspondingly to the position of the communication satellite on an orbit, which is a communications partner, and carries out microwave communication with the communication satellite. This type of antenna apparatus is installed in a control center on the ground, and in addition, there is a case where it is used for an SNG (Satellite News Gathering) system in which it is mounted in a moving vehicle and carries out communication with a parent station through a communication satellite, or is mounted in a ship or an aircraft and is used.
For example, a structural example of a conventional antenna apparatus of this type is disclosed in Japanese Patent Laid-Open No. 175716/1993. In this conventional antenna apparatus, a horizontal stabilizing base is provided to be rotatable about a longitudinal shaft by a stationary shaft and a rotary shaft fitted to each other, and it is supported on the horizontal stabilizing base rotatably in the elevation angle direction, and an antenna is provided on this horizontal stabilizing base rotatably in the elevation angle direction. In this conventional antenna apparatus, a control signal for elevation angle driving is transmitted from the side of the stationary shaft to the side of the horizontal stabilizing base through a slip ring provided around the longitudinal shaft, and the antenna can be rotated in the elevation angle direction by an elevation angle rotation driving portion provided on the horizontal stabilizing base. Since an RF signal for antenna transmission and reception is transmitted to the side of the horizontal stabilizing base through a rotary joint, the horizontal stabilizing base for mounting the antenna is structured to be capable of endless rotating with respect to the stationary side.
Japanese Patent Laid-Open No. 199924/1997 discloses another structural example of a conventional antenna apparatus. This conventional antenna apparatus includes such a structure, as a driving mechanism for rotating an antenna in the elevation angle direction, that a main shaft is coupled with an arm for holding the antenna, a hinge is provided at an intermediate portion between the antenna and the main shaft, and the main shaft is moved vertically by an elevation angle rotating motor provided at a stationary side. The rotation of the elevation angle rotating motor is converted into a linear movement to move the main shaft vertically by a rack and pinion mechanism, and the antenna can be rotated in the elevation angle direction around the hinge by the vertical movement of the main shaft.
In the conventional antenna apparatus disclosed in Japanese Patent Laid-Open No. 175716/1993, since the elevation angle rotation driving portion is provided on the horizontal stabilizing base, in order to transmit the control signal to the elevation angle rotation driving portion from the stationary side, it is necessary to dispose the slip ring around the longitudinal shaft. This slip ring has such a structure that a ring-like electrode provided on one of the stationary shaft and the rotary shaft is brought into contact with a brush provided on the other, and is an electric part in which abrasion occurs between the ring-like electrode and the brush. In an aircraft and a ship, or also in a moving vehicle or the like, a communication equipment is often required to have high reliability, and there has been a problem that the reliability of the antenna apparatus is lowered by the slip ring used in the conventional antenna apparatus.
Besides, in the conventional antenna apparatus disclosed in Japanese Patent Laid-Open No. 199924/1997, the elevation angle rotating motor is disposed at the stationary side, and a slip ring as in the antenna apparatus disclosed in Japanese Patent Laid-Open No. 175716/1993 is not included. However, in order to rotate the antenna in the elevation angle direction, it becomes necessary to move the main shaft vertically, and there has been a problem that the antenna apparatus is enlarged by the vertical linear movement stroke of the main shaft. The linear movement stroke can be shortened by decreasing the distance between the hinge portion of the antenna and the main shaft, however, in that case, a torque for antenna driving becomes high, and the elevation angle rotating motor provided at the stationary side becomes large. Besides, when attention is paid to a holding force for holding the antenna position against a disturbance torque due to wind force applied to the antenna or vibration, since a speed reduction ratio can not be ensured by the rack and pinion provided on the main shaft, it is necessary that the motor is enlarged to increase the holding torque, or a gear having a high speed reduction ratio is provided between the rack and pinion and the elevation angle rotating motor to increase the holding torque. There arise a problem of enlargement of the elevation angle rotating motor in the former case and a problem of enlargement of the gear portion or accuracy thereof in the latter case. In this respect, in this type of antenna apparatus mounted especially in an aircraft or a ship, or in a moving vehicle or the like, high reliability and miniaturization/lightening of the antenna apparatus is required.
The present invention has been made to solve the foregoing problems, and an object thereof is to provide an antenna apparatus which can be miniaturized without using a slip ring for ensuring electrical connection between a stationary portion and a movable portion.
According to a first aspect of the present invention, an antenna apparatus includes a base portion, a first rotary member supported on the base portion and provided rotatably about an azimuth axis, a first motor provided on the base portion and for rotating the first rotary member, a second rotary member supported on the base portion and provided rotatably about a same axis as the first rotary member, a second motor provided on the base portion and for rotating the second rotary member, a relative rotary shaft provided on the first rotary member and rotating by relative rotation between the first rotary member and the second rotary member, and a rotation transmission portion for rotating an antenna provided on the first rotary member about an elevation angle axis by the rotation of the relative rotary shaft.
According to a second aspect of the present invention, in the antenna apparatus of the first aspect, the second rotary member includes gear teeth formed on a circumference around its rotary axis, and the relative rotary shaft includes a gear provided at one end of the shaft and engaging with the gear teeth.
According to a third aspect of the present invention, in the antenna apparatus of the first aspect, the relative rotary shaft includes a shaft member substantially parallel to the azimuth axis, and the rotation transmission portion includes a bevel gear provided at one end of the shaft member, and a bevel gear provided on an elevation angle rotary shaft of the antenna provided on the first rotary member.
According to a forth aspect of the present invention, in the antenna apparatus of the first aspect, the second motor carries out drive control on the basis of an elevation angle setting table describing the relative rotation between the first rotary member and the second rotary member corresponding to an elevation angle of the antenna.
According to a fifth aspect of the present invention, an antenna apparatus includes a base portion, a first rotary member supported on the base portion and provided rotatably about an azimuth axis, a first motor provided on the base portion and for rotating the first rotary member, a second rotary member supported on the base portion and provided rotatably about a same axis as the first rotary member, a second motor provided on the base portion and for rotating the second rotary member, an antenna provided on the first rotary member and rotatably supported about an elevation angle axis, and a link member for connecting a support point provided at a position of the antenna offset from the elevation angle axis and a support point provided on the second rotary member and for rotating the antenna about the elevation angle axis by relative rotation between the first rotary member and the second rotary member.
According to a sixth aspect of the present invention, in the antenna apparatus of the fourth aspect, the link member includes spherical seat bearings at both its ends.
According to a seventh aspect of the present invention, in the antenna apparatus of the first or fourth aspect, the second motor carries out drive control on the basis of an elevation angle setting table describing the relative rotation between the first rotary member and the second rotary member corresponding to an elevation angle of the antenna.
According to the invention of the first to seventh aspects of the present invention, since the antenna can be rotated about the azimuth axis and the elevation angle axis by the motor provided on the base portion, it is not necessary to provide a slip ring of an abrasion part as in the prior art, and high reliability and miniaturization of the antenna apparatus can be realized.